Children's life choices can be influenced by not only parents and peers but also brothers and sisters, as experts are now recognising. Olga Wojtas reports.
As the US presidential election heats up, New York University sociologist Dalton Conley sees one area where the Republican and Democrat rhetorics match - their devotion to family values. Conley, director of NYU's Centre for Advanced Social Science Research, says family is seen as "a sheltered port from the maelstrom of social forces that rip through our lives", with each family member starting out on an equal footing.
But siblings often diverge dramatically in terms of careers and income: one study shows that differences between siblings account for 75 per cent of all differences between individuals. Conley says: "If you attended college, there is almost a 50 per cent chance that one of your siblings did not."
In his new book The Pecking Order: Which Siblings Succeed and Why , he argues that there are three levels of change that create differences between siblings. The first is social or economic change across society, such as the 1960s countercultural revolution. Then there are changes in the family as a whole, such as bereavement or divorce, to which children react idiosyncratically. And there are events such as accidents that affect an individual child.
Malcolm Hill, director of Glasgow University's Centre for the Child and Society, welcomes the challenge to the widespread assumption that parents are the key determinant of how children turn out.
"It's a highly complex picture. Siblings don't have uniform experiences within the same family," he says. "There is perhaps an assumption that somehow a parent is inherently good or bad, or effective or ineffective, whereas in most cases they may just be different with one child than with another. I think parents vary what they do according to the child's age and temperament."
Stirling University sociology lecturer Samantha Punch says Conley's views are refreshing and sensible. "People think children are quite passive, but they can make active decisions," she says. "Sometimes they seem to be striving to do similar things but at other times, striving quite deliberately to do different things."
Hill says de-identification, where siblings are keen to emphasise their separate identity, is common. "A younger brother or sister doesn't want to do something because that's what [the older sibling] does. Some of it is about not wanting to be compared if the other is very successful."
Punch's research focuses on families with three siblings aged between five and 17, and she says there are no clear patterns of influence. Adults may intervene in squabbles on behalf of the younger children because they think they lack power. "But the youngest have definite strategies, and if the parents overcompensate, the oldest can get resentful."
Punch, who has three siblings, says different alliances form in response to different things. She and her sister shared an interest in hobbies and dance, ignored by her brothers, while she and her younger brother went to university, which the others didn't.
She agrees with Conley that siblings' ages at a particular event lead to different reactions. Her parents split up when she was 11, and she and her elder brother "slotted into the second parent role and looked after our younger brother and sister". Her younger siblings are less inclined to maintain contact with their father, not remembering him at home, she says.
Fran Wasoff, US-born director of Edinburgh University's Centre for Research on Families and Relationships, adds that siblings' development depends not only on the family's wishes but also external conditions. Her parents emigrated from Eastern Europe to the US and encouraged her and her sister, now a well-paid banker, to study, but they wouldn't have been able to without free university education. "As a working-class family, had we had to pay $30,000 (£17,000) a year, it would have been beyond our means."
The Pecking Order: Which Siblings Succeed and Why is published by Pantheon Books, £11.85.
A TALE OF TWO CHILDREN ... AND OF TWO DIFFERENT PATHS
Bruce Kettle, 51, Asda baker
"My father was an immigration officer, so we moved a lot and were born in different places. Ann is the eldest, then John, then me, then Peter.
"I didn't really know Ann that well. When she started at Oxford University, I would have been six. I was born in Sussex, then we moved to Middlesex and then to Southampton when I was eight. We lived in a hotel for the first three months. I went to a rough inner-city school.
"Then we moved to Bitterne (a Southampton district), where I still live.
"The rest of the family have travelled far and wide, but I haven't. Not going to university probably made a difference. The other three went to Oxford. Ann has always stood out as the guiding light intellectually. My parents were proud of her. To some extent, she was a hard act to follow.
"I think my parents were a bit disappointed because I wasn't that great academically. My mother got me to do homework when I was keen to go to the youth club.
"I applied to university and got an offer, but I didn't particularly want to go. I was in a relationship and no way would she have gone to university.
"I became an insurance claims inspector. Perhaps because of the achievements of my brothers and sister, I was always keen to do the best I could. But that wasn't all that great for my health. I left the company at 49 with a disability pension.
"I signed up for a part-time bakery course at Southampton City College. I found breadmaking hugely enjoyable, and I've now got a part-time job at the Asda in-store bakery. At college, I helped a lot of the youngsters with the theory part of the course, and one of the lecturers suggested I come in as support. I decided not to because I enjoy this practical work and having the chance to pursue other interests.
"I've got no regrets about not going to university. Ann loves what she does and is obviously good at it, but it's not something I would aspire to."
Ann Kettle, 64, senior lecturer in medieval history, St Andrews University
"I was the first of the family to go to university. My father would have liked to, but he couldn't afford it because his father was a dockyard policeman.
"I don't think I would have gone into higher education if we hadn't moved around because of my father's job in the immigration service.
"I went to a school in Sussex where nice girls didn't go on to university, but when my father worked at London Airport, I went to a mixed grammar school where I was encouraged to apply to Oxford. I got a scholarship before I sat A levels. I could go to university because I didn't need to ask my parents for money.
"All three of my brothers went to a good school, the King Edward VI grammar in Southampton, and probably my brothers John and Peter did well in the Oxford entrance exam because the school encouraged them.
"After Oxford, I did two years' research and then went into what would now be called a contract research job at London University.
"I was lucky to get a job at St Andrews University in the post-Robbins expansion. As well as the usual teaching and research, I've been hebdomadar, responsible for student welfare and discipline, and dean of arts.
"I was president of the Association of University Teachers Scotland and served on the Garrick committee (the Scottish arm of Dearing) and the Scottish Higher Education Funding Council.
"I admire Bruce greatly. He never left Southampton, and so he had the burden of looking after my parents.
"I think he's got the work-life balance right, which I never have. I envy him for making a career change in his late 40s. That would be more or less impossible for an academic.
"If I had to decide again what direction my career would take, I would probably choose the civil service because I'm convinced that universities are institutionally sexist."